Brassieres have been used for lifting and shaping the breasts for approximately 100 years. Brassieres (and other related garments, such as underwire swimwear tops) are typically manufactured using two U-shaped metal components or “underwires,” which serve to create a rounded housing for each breast. The underwire also serves to create a uniform shape in accordance with a fashionable silhouette. The underwire is conventionally a flat U-shape, and does not conform to the curved dimensions of the wearer's rib cage. Thus, the underwire brassiere in its traditional form frequently creates areas of poking and rubbing at the ends of the wire (between breasts and in underarm areas), as well as pinching at the lowermost point of the underwire (at the bottom of the breast, directly under the nipple) where the underwire pushes into the ribs. The larger the breasts, the more significant these pressure points tend to be. Seams and fabric casements, which serve to hold the underwire in place, can further exacerbate the pinching and rubbing of the wire against the skin and ribs.
The underwire casement of traditional brassieres typically attaches to three straps. The primary back strap attaches laterally around the rib cage, in most cases fastening in the rear near the spine. The two shoulder straps attach to the underwire casement in the front and to the lateral strap in the rear. The two shoulder straps run over the belly of the trapezius muscles and support the weight of the breasts against these muscles of the neck and shoulders (primarily the trapezius and levator scapulae muscles). In this way, the force of the lifted breast effectively hangs from the neck and shoulders.
In typical brassiere construction, and especially in larger breasted wearers, all three straps typically create discomfort for the wearer. To support the load of the breast tissue, conventional shoulder straps push down on the trapezius muscles, which in turn forces the head forward and the spine out of proper postural alignment. This misalignment frequently results in tension in the head, neck and shoulders that is directly linked to wearing a conventional bra. This pressure on the trapezius muscles is made visible in the surface indentations frequently left behind in the shoulders of brassiere wearers. Further, these indentations frequently become permanent after years of continued brassiere wear. The effects can also be seen in the slouched or hunched spinal posture of large-breasted, brassiere-wearing women.
In addition, if the primary back strap is fitted tightly enough to the torso such to relieve some of the pressure from the shoulder straps, then the pressure of the underwire casement against the body (and the rubbing and pinching related to the casement) in turn increases. In the case of brassiere garments where the shoulder straps have been removed entirely (i.e. “strapless” brassieres), the garment typically slides down the torso over time, moving out of its intended placement and flattening the profile of the breasts, with aesthetically displeasing results. The result is that wearers are forced to frequently tug the garment back into place, undermining the intention of the wearer for the state of their undergarment to remain private. (Imagine, by way of example, a bride with a strapless dress and strapless brassiere, which begins to fall down during her wedding ceremony. To remain modest and avoid embarrassment, she has no choice but to tug her undergarment back into place, thus revealing the state of her undergarment slippage to any who are observing her.)
In addition, underwire-alternative brassieres that possess rigid regions or thick seams directly beneath the breast fail to provide a comfortable alternative because of resulting pressure on the top of the abdominal cavity when the wearer sits or otherwise bends at the waist.
In summary, the traditional construction of the bra brings with it a set of specific design features that are inherently linked to chafing, rubbing, poking, and pinching of the skin; tension and pain in the muscles of the wearer; and pressure or compression of the upper abdominal cavity.